Magneto-resistive effect type head

ABSTRACT

In a magneto-resistive effect type head having provided between a lower shield layer and an upper shield layer an MR sensor with a magneto-resistive effect or a gigantic magneto-resistive effect; electrode layers electrically connected to the MR sensor; and lower and upper insulating layers mangetically and electrically isolating the MR sensor and the electrode layer from the shield layers, when the gap length is reduced and the lower and upper insulating layers are decreased in thickness, the insulating layers are more liable to a dielectric breakdown by static electricity produced in the manufacturing process of the magnetic head. In a magneto-resistive effect head, the portion of the insulating layer in which the MR sensor  30  and the lower or upper shield layer  10  or  60  do not face each other (in other words, the second lower insulating layer  22  or the second upper insulating layer  52 ) is formed by a lower-resistivity insulating film than the other portion of the insulating layer in which the MR sensor and the layers  10  or  60  face each other (in other words, the first lower insulating layer  21  or the first upper insulating layer  51 ). If electric charge accumulates in the electrode layer or shield layer by static electricity, a minute current flows through the low-resistivity insulating film, reducing a potential difference between the electrode layer and the shield layer and therefore the insulating layers can be prevented from breaking by static electricity.

BACKGROUND OF THE INVENTION

The present invention relates to a magneto-resistive effect type headfor reading an information signal from a magnetic medium and moreparticularly to a magneto-resistive effect type head having a structurecapable of preventing the destruction of the insulation layer by staticelectricity.

With the down-sizing and performance improvement of the magneticrecording apparatuses in recent years, the magneto-resistive effect typehead (hereafter referred to as the MR head) utilizing themagneto-resistive effect is used as the head for reading an informationsignal from the magnetic medium. FIG. 1 shows an example of the MR head.The MR head has a composite structure including a recording head 1utilizing electromagnetic induction to write information and areproducing head 2 utilizing a magneto-resistive effect (MR) or a giantmagneto-resistive effect (GMR) to read the information signal from themagnetic medium.

FIG. 2 shows an example of the reproducing head in a view facing themagnetic medium. The reproducing head includes an MR sensor 30,electrode layers 40, a lower insulating layer 20, and an upperinsulating layer 50, which are all disposed between a lower shield layer10 and an upper shield layer 60. Generally, the bias layers 45 to applya vertical bias magnetic field to the MR sensor 30 are provided on bothsides of the MR sensor 30 (Normally, the bias layers and the electrodelayer are formed successively).

The lower insulating layer 20 and the upper insulating layer 50 performsthe function to magnetically and electrically isolate the MR sensor 30from the lower shield layer 10 and the upper shield layer 60. As thematerial for the insulating layers, an aluminum oxide (alumina) film isgenerally used which is non-magnetic and superior in electricalinsulating properties. The space where the MR sensor 30 is disposedbetween the lower shield layer 10 and the upper shield layer 60 isdefined as a gap length GL. In a magnetic recording apparatus, the gaplength GL is an important parameter related to bit length.

SUMMARY OF THE INVENTION

Magnetic recording apparatuses are becoming smaller and improving inperformance year by year and accordingly the gap length GL of thereproducing head to read information is becoming narrower. Inconsequence, the trend of the lower insulating layer 20 and the upperinsulating layer 50 has been toward a thinner film thickness.

As the lower insulating layer 20 and the upper insulating layer 50become narrower, those insulating layers are liable to dielectricbreakdown due to static electricity produced in the magnetic headmanufacturing and assembling processes. Measures have been taken toprevent static electricity from accumulating in the magnetic headmanufacturing and assembling processes. However, it is impossible toachieve complete prevention of dielectric breakdown caused by staticelectricity in those processes. Therefore, the structure of the magnetichead must be so formed as not to suffer dielectric breakdown even ifstatic electricity is produced to some extent.

JP-A-07-65324 (U.S. Pat. No. 5,539,598) and JP-A-07-65330 disclosemethods in which the shield layer and the electrode layer are shortedelectrically.

Moreover, JP-A-08-221720 (U.S. Pat. No. 5,375,022) reveals a method inwhich the shield layer and the electrode layer are connected by ahigh-resistivity magnetic material. Those methods, when staticelectricity occurs, bring the MR sensor 30 and the shield layer to thesame potential when static electricity occurs to thereby prevent abreakdown of the insulating layers between the MR sensor and the shieldlayers. However, there is a decrease in output because the sense currentsplits from the electrode layer and flows to the shield layers even whenthe magnetic head is operating in the reproducing apparatus.

An object of the present invention is to provide a magneto-resistiveeffect type head of a structure capable of preventing a breakdown of theinsulating layers between the MR sensor and the shield layersattributable to the occurrence of static electricity even when the gaplength is made narrow.

Another object of the present invention is to provide amagneto-resistive effect type head of a structure in which the sensecurrent does not shunt from the electrode layer and flows into theshield layers even when the magnetic head according to the presentinvention is mounted in a magnetic recording apparatus as shown in FIG.9 and put into operation.

In the magneto-resistive effect type according to the present invention,the portions of the insulating films in which the MR sensor and thelower and upper shield layers do not face each other are formed by aninsulating film with a lower resistivity than the other portions of theinsulating films in which the MR sensor and the lower and upper shieldlayers face each other.

According to an aspect of the present invention, a magneto-resistiveeffect type head comprises between a lower shield layer and an uppershield layer:

an MR sensor including a thin film having at least a magneto-resistiveeffect or a gigantic magneto-resistive effect,

bias layers for applying a longitudinal bias magnetic field to the MRsensor, and

electrode layers for supplying a detection current to the MR sensor, and

a lower insulating layer between the MR sensor and the lower shieldlayer and an upper insulating layer between the MR sensor and the uppershield layer, the two insulating layers being located at that part ofthe head which faces a magnetic medium,

wherein portions of the lower and upper insulating layers in which theMR sensor and the lower and upper shield layers do not face each otherhave a lower resistivity than the other portions of the lower and upperinsulating layers in which the MR sensor and the lower and upper shieldlayers face each other.

According another aspect of the present invention, in themagneto-resistive effect type head, the lower-resistivity portions ofthe insulating layers in which the MR sensor and the shield layers donot face each other exclusive of the other portions of the insulatinglayers in which the MR sensor and the shield layers face each other maybe set either between the MR sensor and the lower shielding layer orbetween the MR sensor and the upper shielding layer. Namely, either allover the insulating layer between the MR sensor and the lower shieldinglayer or all over the insulating layer between the MR sensor and theupper shielding layer is formed of an insulating film with lowresistivity.

The low-resistivity portions of the insulating layer in which the MRsensor and the lower and upper shield layers do not face each other arepreferably formed by a nitride or an oxy nitride of aluminum, silicon ora mixture of those elements.

This low-resistivity insulating layer preferably has a characteristicthat the resistivity at an applied electric field of 3 MV/cm is lessthan {fraction (1/1000)} of the resistivity at an applied electric fieldof 1 MV/cm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an example of a conventional magneto-resistiveeffect type head structure;

FIG. 2 is a view of the reproducing head as a conventionalmagneto-resistive effect type head as seen from the surface of amagnetic medium facing the reproducing head;

FIG. 3 is a diagram showing the resistivity versus electric fieldcharacteristics of silicon nitride;

FIG. 4 is a diagram showing the resistivity versus electric fieldcharacteristics of alumina;

FIGS. 5A and 5B are sectional views in the depth direction of thereproducing head part of the magneto-resistive effect type headstructure according to a first embodiment of the present invention;

FIGS. 6A to 6G are the manufacturing process steps of the reproducinghead part of the magneto-resistive effect type head structure accordingto the first embodiment of the present invention;

FIGS. 7A and 7B are sectional views in the depth direction of thereproducing head part of the magneto-resistive effect type headstructure according to a second embodiment of the present invention;

FIGS. 8A and 8B are pattern diagrams after the formation of the uppershield layer of the reproducing head part of the magneto-resistiveeffect type head structure according to a third embodiment of thepresent invention; and

FIG. 9 is a schematic diagram of a magnetic recording apparatus.

DESCRIPTION OF THE EMBODIMENTS

FIG. 3 shows the resistivity versus electric field characteristics ofsilicon nitride as an example of a low-resistivity insulating film. Forcomparison's sake, FIG. 4 shows the resistivity versus electric fieldcharacteristics of alumina currently widely used in the upper and lowerinsulating layers. Note that the electric field here is a value obtainedby dividing the applied voltage by the film thickness. In the case ofalumina, even when the electric field is increased, the resistivitychanges by two to three orders of magnitude.

For silicon nitride, the resistivity decreases as an exponentialfunction as the electric field is increased. For example, when theelectric field is 1 MV/cm and 3 MV/cm, the resistivity is of alumina10¹⁵Ω·cm and 10¹⁴Ω·cm. On the other hand, the resistivity of siliconnitride is 10¹²Ω·cm and 10⁸Ω·cm. In other words, when the electric fieldis 1 MV/cm, the resistivity of silicon nitride is smaller by threeorders of magnitude than for alumina, but when the electric field is 3MV/cm, the resistivity of silicon nitride is smaller by six orders ofmagnitude than with alumina. Among materials, such as silicon nitride,the resistivity of which decrease as an exponential function withincreasing electric field are AlN, Si—Al—N, Si—Al—N—O, SiC, DLC and soon. Oxide insulating materials very deficient in oxygen exhibit similarelectric characteristics.

By utilizing a difference in resistivity between the insulating films,it is possible to manufacture a head free of destruction of theinsulating layers caused by static electricity. More specifically, ahigh resistivity insulating film, such as alumina, is used where thefilm thickness must be thin while the insulating properties aremaintained. On the other hand, where there is not a strict definitionfor film thickness, it is only necessary to use a low-resistivityinsulating film, such as silicon nitride, in the insulating layer placedbetween an electrode layer and a shield layer or between a metal layersuch as these and another metal layer electrically connected to such ametal layer. For example, when there is a high potential differencebetween a shield layer and an electrode layer attributable to staticelectricity or the like, the silicon nitride under a high voltagedecreases in resistivity by several orders of magnitude than alumina (adecrease by six orders of magnitude in resistivity when the electricfield is 3 MV/cm). Therefore, a leak current flows through thelow-resistivity insulating film, so that the potential differencebetween the shield layer and the electrode layer can be reduced.Consequently, the insulating layers can be prevented from sufferingdielectric breakdown. Moreover, the larger the area of the metal layershaving the low-resistivity insulating film held therebetween, the moreeasily the leak current flows. The low-resistivity insulating film isrequired to have a thickness large enough not to suffer a dielectricbreakdown.

When a head structured as described is mounted as is in the magneticrecording apparatus and put into operation, the silicon nitride has aninsulation resistance close to that of alumina in the ordinary operationrange. Therefore, it never occurs that a sense current leaks to theshield layer and gives rise to noise.

FIGS. 5A and 5B a first embodiment of the present invention. FIGS. 5Aand 5B indicate cross sections taken along planes A and B of themagnetic head depicted in FIG. 1.

A portion of the insulating layer in which at least the MR sensor 30 andthe lower shield layer 10 face each other (in other words, the firstlower insulating layer 21) and another portion of the insulating layerin which at least the MR sensor 30 and the upper shield layer 60 faceeach other (in other words, the first upper insulating layer 51) areformed by a high-resistivity insulating film, such as Al₂O₃, SiO₂ or amixture of them and the other portions of the insulating layers (inother words, the second lower insulating layer 22 and the second upperinsulating layer 52) are formed by a low-resistivity insulating film,such as silicon nitride. The first lower insulating layer 21 and thefirst upper insulating layer 51 are the portions whose thickness isbecoming thinner with progressively higher integration in magneticrecording apparatuses. Therefore, it is necessary to prevent the currentflowing through the MR sensor 30 and the electrode layer 40 from beingdivided and flowing through the above-mentioned portions even If thefilm thickness is made thinner. It is also necessary to increasestrength against dielectric breakdown by static electricity. Meanwhile,there is no stringent prescription for the second lower insulating layer22 and the second upper insulating layer 52. If a low-resistivityinsulating film, such as silicon nitride, is used for the second lowerinsulating layer 22 and the second upper insulating layer 52 to letexcess charge such as static electricity, when it occurs, move throughthe second lower insulating layer 22 and the second upper insulatinglayer 52 to the adjacent metal layers, then a large potential differencedoes not occur among the lower shield layer 10, the electrode layer 40,the MR sensor 30 electrically connected to the electrode layer 40, andthe upper shield layer 60. Consequently, even if the first lowerinsulating layer 21 and the first upper insulating layer 51 are madethin, dielectric breakdown hardly occurs in the first lower insulatinglayer 21 and the first upper insulating layer 51.

An example of a method of manufacturing this head will be described inthe following. FIGS. 6A to 6E show the process steps of the patterns ona substrate.

A lower shield layer 10 (Sendust, Fe—Ni, or the like) is formed on asuitable substrate. A first lower insulating layer 21 is formed. Thisinsulating layer 21 has as its main object to provide an electrical andmagnetic insulation of the MR sensor 30 from the lower shield layer 10and is formed by Al₂O₃, SiO₂ or a mixture of them. On top of theinsulating layer 21, an MR sensor film is formed. The MR sensor 30 is asensor utilizing a magneto-resistive effect or a giant magneto-resistiveeffect. The first lower insulating layer 21 and the MR sensor 30 aredeposited tentatively on the whole upper surface of the substrate. Othermethods, such as resist and ion milling, may be used to form desiredpatterns. A resist pattern in a stencil form is made to form bias layers45 and first electrode layers 41 in specified positions. The MR sensorfilm is shaped by ion milling with this resist pattern as a mask, andthen bias layers 45 and a first electrode layer 41 are formed. For thefirst electrode layer, a high refractory metal, such as Ta, is used froma viewpoint of electromigration. Or otherwise, the first electrode layer41 may be formed by a material with a low resistivity, such as Au or Al.Subsequently, the resist is removed by a resist stripping solution. FIG.6A shows the condition after the resist has been removed.

A resist pattern in a stencil form is created to pattern the MR sensor30 to a specified shape and to remove excesses of the first lowerinsulating layer 21. Excesses of the MR sensor and the first lowerinsulating film are removed by ion milling or the like with thisresist-pattern mask. Or otherwise, after the MR sensor 30 has beenshaped to a specified pattern, it is possible to remove the resist andcreate a resist-pattern mask to remove excesses of the first lowerinsulating film. After excesses of the first lower insulating film havebeen removed, a second lower insulating layer 22 is deposited by usingthe same resist pattern. As the material for this insulating layer 22, alow-resistivity insulating film mentioned above is used. There is nostrict definition for film thickness. It is only required that ahigh-quality film be formed in a stable manner. In the presentinvention, the film is deposited to a thickness of 100 nm or so.Afterwards, the resist is removed. FIG. 6B shows the condition after theresist has been removed.

To connect the first electrode layers 41 to terminals, second electrodelayers 42 are formed (FIG. 6C). The second electrode layers arepreferably made of a low-resistivity material, such as Au, Al or Cu. Thesecond electrode layer 42 is formed on top of the second lowerinsulating layer 22.

A resist pattern in a stencil form is created for use in forming thefirst upper insulating layer 51 in a specified position, and by usingthis resist pattern, a high resistivity insulating film, such as Al₂O₃or SiO₂, is formed. Or otherwise, it is possible to form the first upperinsulating layer 51 on the whole surface of the substrate and thencreate a specified pattern by using a resist pattern or by ion milling,for example. Note that when forming the first upper insulating layer 51,the parts forming the electrode terminal 63 is protected by a resistpattern to prevent it from being deposited by a high-resistivityinsulating film. FIG. 6D shows the condition after the first upperinsulating layer 51 of a specified shape has been formed.

With a resist pattern formed on the first upper insulating layer 51 andthe parts forming the electrode terminal 63, the second upper insulatinglayer 52 is formed. To this end, a low-resistivity insulating materialis used. For the same reason as mentioned about the second lowerinsulating layer 22, the second upper insulating layer 52 is depositedto a thickness of 100 nm. Afterwards, the resist is removed.

The upper shield layer 60 is formed. FIG. 6E shows the condition afterthe upper shield layer 60 has been formed.

FIGS. 6F and 6G are sectional views taken along the lines A-A′ and B-B′,respectively (Note that those drawings do not show the portion of thesubstrate to be cut away when the magnetic head is mounted on theslider.). In the above-mentioned method, a high-resistivity insulatingfilm is used for at the portion in which at least the MR sensor 30 andthe lower shield layer or the upper shield layer face each other, andthere is no worry about noise caused by current splitting. Furthermore,because the lower shield layer 10, the second electrode layer 42 whichare electrically connected to the MR sensor 30 and the upper shieldlayer 60, are connected through low-resistivity insulating films, evenif static electric charge accumulates in the shield layer or theelectrode layer, a leak current flows through the low-resistivityinsulating film, thus reducing a potential difference and decreasingchances of dielectric breakdown. This low-resistivity insulating film,when it is under a low voltage at which the magnetic head is operatingin the magnetic recording apparatus, has a high resistivity close tothat of a high-resistivity insulating film, such as alumina, in otherwords, a much higher resistivity than metals. Therefore, it never occursthat a current splits from the electrode layer and flows to the shieldlayer.

FIGS. 7A and 7B show a second embodiment of the present invention. FIGS.7A and 7B, like in FIGS. 5A and 5B, indicate the cross sections takenalong the planes A and B of the magnetic head shown in FIG. 1.

The second embodiment is a case of using a low-resistivity insulatingfilm for the whole lower insulating layer or for the whole upperinsulating layer. In this case, a low-resistivity insulating film shouldpreferably be used for the whole lower insulating layer or the wholeupper insulating layer by considering the insulation properties of thematerial used and a decrease of breakdown voltage due to the decrease infilm thickness of the stepped portion of the magnetic head. Theadvantage of this method is that the manufacturing process can be madeshorter than in the first embodiment. Let us consider how to use alow-resistivity insulating film for the lower insulating layer. In thefirst embodiment, because the second lower insulating layer is formed,the first lower insulating layer must be formed in a specified shape. Incontrast, if a low-resistivity insulating film is used for the lowerinsulating layer as a unified layer, the process for forming the firstand second insulating layers into specific shapes can be shortened.

Description will proceed to a third embodiment of the present invention.

If the area of the metal layers holding a low-resistivity insulatingfilm between them is large, a minute current flowing through thelow-resistivity insulating film amounts to much, thus decreasing chancesof incurring dielectric breakdown by static electricity. Therefore, thearea should be wide for the shield layer and the electrode layer holdingthe low-resistivity insulating layer between them. However, for somereasons, it may become necessary to make the area of the shield layersmall. Description will be made of an example where the area of theupper shield layer is made small.

FIG. 8A shows the condition when the head structure has been formed upto the upper shield layer whose area is reduced (which corresponds tothe magnetic head in FIG. 6F according to the first embodiment. Theupper shield layer 60 is in a small shape specified for some reasons. Atlower right of the drawing, a terminal 61 is formed by using alow-resistivity insulating layer, and the terminal 61 performs thefunction to reduce potential difference between the upper shield layer60 and the second electrode layer 42.

In addition, a wiring pattern 62 is formed by connecting the uppershield layer 60 to the terminal 61 so as to make the upper shield layer60 and the terminal 61 equipotentials each other. No specific propertiesexcept high electric conductivity are required for the materials formingthe terminal 61 and the wiring pattern 62. If the same material as withthe upper shield layer 60 is used for the terminal 61 and the wiringpattern 62, these parts can be formed easily and simultaneously with theprocess of forming the upper shield layer 60. The second electrode layer42 needs to be so formed as to face the terminal 61 through theintermediary of a low-resistivity insulating film. The second electrodelayer 42 may be expanded so as to face the terminal 61 as shown in FIG.8A for example.

FIG. 8B shows a cross section taken along the line C—C in FIG. 8A (Notethat this drawing does show the portion to be cut away when the magnetichead is mounted on the slider.). The upper shield layer 60 is, only in asmall area thereof, in contact with the low-resistivity insulating filmbut the terminal 61 in a wide area thereof faces the second electrodelayer 42 through the intermediary of the low-resistivity insulatingfilm. Therefore, if electric charge, such as static electricity, isstored in the upper shield layer 60, a minute current flows through theterminal 61 and the second upper insulating layer 52 to the secondelectrode layer 42. In consequence, a potential difference between theshield layer 60 and the second electrode layer 42 (the first electrode41 and the MR sensor 30 electrically connected the electrode layer 42)is reduced, thus decreasing chances of dielectric breakdown. In thethird embodiment, the upper shield layer 60 is, only in a small area, incontact with the low-resistivity insulating film, but may be without anycontact with the low-resistivity insulating film at all so long as thearea of the terminal 61 is sufficiently large.

As has been described, by forming a portion of the insulating layer inwhich the MR sensor 30 and at least the lower shield layer or the uppershield layer face each other by a high-resistivity insulating film andforming the other portion of the insulating layer in which the MR sensor30 and the lower shield layer or the upper shield layer do not face by alow-resistivity insulating film, even if excess static charge is storedin the lower shield layer, the electrode layer (or the MR sensor) or theupper shield layer, a minute current flows through the low-resistivityinsulating film, thus enabling potential differences to be reducedbetween the lower shield layer, the electrode layer (or the MR sensor)and the upper shield layer. This makes it possible to prevent theinsulating layers from suffering dielectric breakdown by staticelectricity. Meanwhile, when there is no excess static electricitystored, the low-resistivity insulating film has a very high resistivitycompared with metals, and therefore it never occurs that a sense currentsplits from the electrode layer and flows into the shield layers, andgives rise to noise.

What is claimed is:
 1. A magneto-resistive effect type head comprisingbetween a lower shield layer and an upper shield layer: an MR sensorincluding a thin film having at least a magneto-resistive effect or agiant magneto-resistive effect, bias layers for applying a longitudinalbias magnetic field to said MR sensor, and electrode layers forsupplying a detection current to said MR sensor, and a lower insulatinglayer between said MR sensor and said lower shield layer and an upperinsulating layer between said MR sensor and said upper shield layer,said two insulating layers being located at that part of said head whichfaces a magnetic medium, wherein portions of said lower and upperinsulating layers in which said MR sensor and said lower and uppershield layers do not face each other have a lower resistivity than theother portions of said lower and upper insulating layers in which saidMR sensor and said lower and upper shield layers face each other.
 2. Amagneto-resistive effect type head according to claim 1, wherein theinsulating film of the portions of said lower and upper insulatinglayers in which said MR sensor and said lower and upper shield layers donot face each other is formed by a nitride or oxy nitride of aluminum,silicon or a mixture of these elements.
 3. A magneto-resistive effecttype head according to claim 1, wherein the insulating film of theportions of said lower and upper insulating layers in which said MRsensor and said lower and upper shield layers do not face each other hasa characteristic that the resistivity at an applied electric field of 3MV/cm is {fraction (1/1000)} or less of the resistivity at an appliedelectric field of 1 MV/cm.
 4. A method for manufacturing amagneto-resistive effect type head set forth in claim 1 comprising thesteps of: forming a lower shield layer on a substrate; forming ahigh-resistivity insulating film on said lower shield layer bysputtering or CVD; etching said high-resistivity insulating film into aspecified shape; forming said MR sensor into a specified shape; forminga low-resistivity insulating film by sputtering or CVD; etching saidlow-resistivity insulating film into a specified shape; and forming saidupper shield layer.
 5. A method of manufacturing a magneto-resistiveeffect type head set forth in claim 1, comprising the steps of: forminga lower shield layer on a substrate; forming a high-resistivityinsulating film on said lower shield layer by sputtering or CVD; etchingsaid high-resistivity insulating film into a specified shape; formingsaid MR sensor into a specified shape; forming a low-resistivityinsulating film in a specified shape by sputtering or CVD with a resistpattern; and forming said upper shield layer.
 6. A method formanufacturing a magneto-resistive effect type head set forth in claim 1,comprising the steps of: forming a lower shield layer on a substrate;forming a high-resistivity insulating film on said lower shield layer ina specified shape by sputtering or CVD with a resist pattern; formingsaid MR sensor into a specified shape; forming a low-resistivityinsulating film by sputtering or CVD; etching said low-resistivityinsulating film into a specified shape; and forming said upper shieldlayer.
 7. A method for manufacturing a magneto-resistive effect typehead set forth in claim 1, comprising the steps of: forming a lowershield layer on a substrate; forming a high-resistivity insulating filmon said lower shield layer in a specified shape by sputtering or CVDwith a resist pattern; forming said MR sensor into a specified shape;forming a low-resistivity insulating film in a specified shape bysputtering or CVD with a resist pattern; and forming said upper shieldlayer.
 8. A magnetic recording apparatus comprising: a magneto-resistiveeffect type head set forth in claim 1; a magnetic recording mediumplaced in a position to face said magneto-resistive effect type head;means for driving said magneto-resistive effect type head; means fordriving said magnetic recording medium; and means for processingrecording/reproducing signals.
 9. A method for forming amagneto-resistive effect type set forth in any of claim 1, comprisingthe steps of: forming a lower shield layer on a substrate; forming afirst lower insulating layer on said lower shield layer in a specifiedshape by sputtering or CVD with a resist pattern; forming a MR sensor ina specified shape; forming a second lower insulating layer in aspecified shape by sputtering or CVD with a resist pattern; and formingsaid upper shield layer.
 10. A magneto-resistive effect type headcomprising between a lower shield layer and an upper shield layer: an MRsensor including a thin film having at least a magneto-resistive effector a giant magneto-resistive effect; bias layers for applying alongitudinal bias magnetic field to said MR sensor; electrode layers forsupplying a detection current to said MR sensor; a lower insulatinglayer between said MR sensor and a lower shield layer and an upperinsulating layer between said MR sensor and an upper shield layer, saidtwo insulating layers being located at that part of said head whichfaces a magnetic medium, wherein a portion of said lower or upperinsulating layer in which said MR sensor and said lower or upper shieldlayer do not face each other has a lower resistivity than the otherportion of said lower or upper insulating layer in which said MR sensorand said lower or upper shield layer face each other, and wherein atotal thickness of the portions of the lower and upper insulating layersin which said MR sensor and said lower or upper shield layer do not faceeach other is greater than a total thickness of the other portions ofsaid lower and upper insulating layers in which said MR sensor and saidlower or upper shield layer face each other.
 11. A magnetic recordingapparatus comprising: a magneto-resistive effect type head set forth inclaim 10; a magnetic recording medium placed in a position to face saidmagneto-resistive effect type head; means for driving saidmagneto-resistive effect type head; means for driving said magneticrecording medium; and means for processing recording/reproducingsignals.
 12. A method for forming a magneto-resistive effect type setforth in claim 10, comprising the steps of: forming a lower shield layeron a substrate; forming a first lower insulating layer on said lowershield layer in a specified shape by sputtering or CVD with a resistpattern; forming said MR sensor in a specified shape; forming a secondlower insulating layer in a specified shape by sputtering or CVD with aresist pattern; and forming said upper shield layer.
 13. Amagneto-resistive effect type head comprising between a lower shieldlayer and an upper shield layer: an MR sensor including a thin filmhaving at least a magneto-resistive effect or a giant magneto-resistiveeffect; bias layers for applying a longitudinal bias magnetic field tosaid MR sensor; a first electrode layer connected to said MR sensor; asecond electrode layer supplying a detection current to said firstelectrode layer; a first lower insulating layer between said MR sensorand said first electrode and said bias layer, and said lower shieldlayer, and a second lower insulating layer between said second electrodelayer and a lower shield layer; a first upper insulating layer betweensaid MR sensor 30 and said first electrode layer and said bias layer,and an upper shield layer; and a second upper insulating layer betweensaid second electrode layer and an upper shield layer, wherein saidsecond lower and upper insulating layers have a lower resistivity thansaid first lower and upper insulating layers, and wherein a totalthickness of said second lower and upper insulating layers is greaterthan a total thickness of said first lower and upper insulating layers.14. A magneto-resistive effect type head according to claim 13, whereinthe insulating film of said second lower and upper insulating layers isformed by a nitride or oxy nitride of aluminum, silicon or a mixture ofthose elements.
 15. A magneto-resistive effect type head according toclaim 13, wherein the insulating film of said second lower and upperinsulating layers has a characteristic that the resistivity at anapplied electric field of 3 MV/cm is {fraction (1/1000)} or less of theresistivity at an applied electric field of 1 MV/cm.
 16. A method formanufacturing a magneto-resistive effect type head set forth in claim13, comprising the steps of: forming a lower shield layer on asubstrate; forming said first lower insulating layer on said lowershield layer by sputtering or CVD; etching said first lower insulatinglayer into a specified shape; forming said MR sensor into a specifiedshape; forming said second lower insulating layer by sputtering or CVD;etching said second lower insulating layer into a specified shape; andforming said upper shield layer.
 17. A method for manufacturing amagneto-resistive effect type head set forth in claim 13, comprising thesteps of: forming a lower shield layer on a substrate; forming a firstlower insulating layer on said lower shield layer by sputtering or CVD;etching said first lower insulating layer into a specified shape;forming said MR sensor into a specified shape; forming said second lowerinsulating layer by sputtering or CVD with a resist pattern; and formingsaid upper shield layer.
 18. A method for manufacturing amagneto-resistive effect type head set forth in claim 13, comprising thesteps of: forming a lower shield layer on a substrate; forming saidfirst lower insulating layer on said lower shield layer in a specifiedshape by sputtering or CVD with a resist pattern; forming said MR sensorin a specified shape; forming said second lower insulating layer bysputtering or CVD; etching said second lower insulating layer into aspecified shape; and forming said upper shield layer.
 19. A magneticrecording apparatus comprising: a magneto-resistive effect type head setforth in claim 13; a magnetic recording medium arranged to face saidmagneto-resistive effect type head; means for driving saidmagneto-resistive effect type head; means for driving said magneticrecording medium; and means for processing recording/reproducingsignals.
 20. A magneto-resistive effect type head comprising between alower shield layer and an upper shield layer: an MR sensor including athin film having at least a magneto-resistive effect or a giantmagneto-resistive effect; bias layers for applying a longitudinal biasmagnetic field to said MR sensor; a first electrode layer connected tosaid MR sensor; a second electrode layer supplying a detection currentto said first electrode layer; a lower insulating layer between said MRsensor and a lower shield layer at that part of said head which faces amagnetic medium; and an upper insulating layer between said MR sensorand an upper shield layer, wherein a portion of said lower or upperinsulating layer in which said MR sensor, said first electrode layer,said bias layers and said lower or upper shield layer do not face eachother is lower in resistivity than the other portion of said lower orupper insulating layer in which said MR sensor, said bias layer and saidlower or upper shield layer face each other, and wherein a totalthickness of the portion of said lower or upper insulating layer inwhich said MR sensor, said first electrode layer, said bias layers andsaid lower or upper shield layer do not face each other is greater thana total thickness of the other portion of said lower or upper insulatinglayer in which said MR sensor, said first electrode layer, said biaslayers and said lower or upper shield layer face each other.